The present invention generally relates to venting and air intake structures for fuel-fired heating appliances and, in a preferred embodiment thereof, more particularly relates to methods of fabricating a vent/intake system, including a specially designed sheet metal colinear-to-coaxial duct transition assembly, for use in conjunction with a fuel-fired, direct vent heating appliance.
Fuel-fired, direct vent heating appliances, such as water heaters, fireplaces and furnaces, are typically provided with a first duct structure through which hot combustion gases from the appliance may be discharged, and a second duct structure through which combustion air may be drawn into the appliance. It is considered desirable for pressure balancing purposes to discharge a direct vent appliance's hot flue gases and draw its combustion air through a "concentric" duct termination structure--i.e., one in which the hot flue gas discharge duct is centrally disposed within a laterally larger combustion air intake duct). However, it is desirable for other purposes, such as preventing overheating of the incoming combustion air and preventing degradation of the appliance burner performance caused by flue gas leaking into the combustion air intake duct, to arrange the flue gas discharge and combustion air intake ducts in a "colinear" arrangement--i.e., one in which the two ducts are run separately from one another, with neither of the two ducts being disposed within the other duct.
Thus, to operatively connect the two colinear ducts to the coaxially arranged termination assembly, through which discharging flue gas and incoming combustion air are simultaneously flowed, the installation between the two ducts and the termination assembly of a coaxial-to-colinear transition conversion assembly is required to properly route the flue gas and combustion air flows between the colinear ducts and the termination assembly. AS conventionally fabricated, this type of conversion assembly is customarily formed from a bendable sheet metal material, with the fabrication of the conversion assembly typically presenting a tedious, relatively complex task which undesirably increases the overall cost of the vent/intake system.
Because of this, a need exists for simpler and less expensive methods of fabricating a vent/intake system for a fuel-fired, direct vent heating appliance, including a colinear-to-coaxial duct transition assembly of the general type described above. It is to this need that the present invention is directed.